There is known a technique of stacking a plurality of boards one above another by insertion-mounting a joining part into through holes formed in the boards. In this case, it is known to use a joining part in which the width of a body portion thereof disposed between the boards is larger than the width of the through holes formed in the boards. In addition, it has been known that, in a case where a plurality of boards is stacked one above another by surface mounting a joining part to the boards, a notch is formed in the joining surfaces of the joining part to be joined with the boards.
In a case where insertion-mounting is performed using a joining part having a body portion which is disposed between the boards and has a width larger than the width of the through holes formed in the boards, voids may be generated when joining members are embedded in the through holes. When the voids are generated, the quality of joining is deteriorated.
The followings are reference documents.
[Document 1] Japanese Laid-open Utility Model Publication No. 61-173145 and
[Document 2] Japanese Laid-open Patent Publication No. 2007-115846 and
[Document 3] Japanese Laid-open Patent Publication No. 2012-028624.